UW experts discuss the earthquake in Turkey and Syria

Three University of Washington experts have provided the following quotes in response to the magnitude 7.8 earthquake that struck Turkey and Syria on Monday morning. 

Harold Tobin is director of the Pacific Northwest Seismic Network and a UW professor of Earth and space sciences. Tobin studies tectonic plate boundaries with a focus on how faults work and the conditions inside them that lead to earthquakes. He also serves as Washington state’s seismologist.

“This region along the East Anatolian Fault has a well-known history of seismic activity, and it had been identified by Turkish emergency management as a place of high seismic hazard,” Tobin said. “However, its known history does not include earthquakes of magnitude 7 or above since seismometers existed to measure them, though historic records indicate earthquakes of up to magnitude 7.4 have occurred. The scale and size of this magnitude 7.8 quake and the one that followed are both larger than what was most likely anticipated. The fact that there was a second large and damaging quake, the magnitude 7.5 that occurred about nine hours later, is not unprecedented globally, but is very uncommon, especially at this size.

“It is not typical for a rupture on one fault to trigger a slip on another fault, but it’s also not that uncommon. For example, the 2019 earthquakes in Ridgecrest, California, also clearly had slip along two different faults.

“The surprising size of the two earthquakes and the length of the fault zone makes them very remarkable events. We have seen very, very few on-land, strike-slip fault earthquakes as large as this in the past century, anywhere. For comparison, the San Andreas Fault in California has not had a comparable quake since the 1906 San Francisco Earthquake. The only other U.S. event of similar scale in the era of instrumental records was the 2002 Denali Fault Earthquake in Alaska. That was also a strike-slip fault, involving the lateral motion of two crustal blocks, as opposed to the converging motion of a subduction zone fault. Fortunately that earthquake affected a sparsely populated region.”

In southern Turkey and Syria, “the risk remains elevated, unfortunately, because aftershocks are expected for some time — weeks to months to even years. Besides the 7.8 and the 7.5, there have been three aftershocks of magnitude 6.0 or larger already, and more can be expected. People in the region need to remain vigilant that more aftershocks may occur. It is also possible, though less probable, that additional, very large earthquakes could occur, even ones as large as, or larger than, the 7.5 and 7.8. Adjacent segments of the faults could still have built-up strain to be released.”

Dawn Lehman, UW professor of civil and environmental engineering, studies older buildings with substandard details and connections to develop advanced computer methods that can identify weak points. She then creates rehabilitation methods to improve the structural performance of these buildings.

“It is devastating to watch the aftermath of this earthquake followed by aftershocks,” Lehman said. “Clearly we have to think about the magnitude of aftershocks and simple mechanisms to reinforce brittle structures.” 

“Although every building is unique in its geometry, function and seismic demands, it is well understood that reinforced concrete buildings without seismic detailing are particularly vulnerable in earthquakes. In modern reinforced concrete design, we improve the seismic performance by using steel with very high strain capacities at fracture and closely spaced hoop-shaped reinforcement to encase the main reinforcing bars. Even if the two buildings have the same strength, only the building with the high-strain capacity steel and the encased rebar will be able to sustain the earthquake demands without collapsing. Otherwise the response is ‘brittle.'”

“Many countries are studying important technologies to prevent building collapse in moderate to large earthquakes. The knowledge and development of the technologies is the first step, but implementation and construction methods are also very important. We have seen over decades that improvement in codes leads to improvement in seismic response.”

“The most important thing right now is the humanitarian aspect of this tragedy: ensuring people who have been displaced have warm shelter and basic human necessities and evacuating structures that have a high probability of collapsing in a large aftershock. I am thankful for every person who is helping with that effort.” 

Mark Ward, lecturer of international studies at the UW, is a retired foreign service officer. His expertise includes humanitarian emergencies, disasters from natural and human causes and public-private partnerships in disaster response.

“Turkish authorities will probably mount an effective response,” Ward said. “They have a lot of experience and international support. The situation in northwest Syria will be far more dire, where the seemingly endless civil war will make emergency response much, much harder.”